This project focuses on the factors which control the in vitro assembly and disassembly of microtubules, in particular the roles of calcium, GTP and water structuring agents such as glycerol and sucrose. Turbidimetry and electron microscopy are used to monitor assembly. A second aspect deals with the neurofilament and the comparison of its chemistry and immunological properties with those of the microtubule and the glial acidic fibrillary protein. A number of animal models are used to study the effects of experimentally induced proliferation of the neurofilaments on neuronal function and to study the ontogeny and transport of the neurofilament subunit. The final aspect is devoted to the characterization of the protein making up the "twisted tubule" or bifilar structures which are characteristic of human senile and presenile dementia. The major protein from fractions enriched in these structures is to be compared immunologically and biochemically with the subunits of the neurofilaments and the neurotubules. Preliminary results indicate that this protein is closely related to, if not identical to, the normal neuronal neurofilament protein.